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Charged particles—such as electrons and protons—create electromagnetic fields when they move, andthese fields transport the type of energy we callelectromagnetic radiation, or light.

A wave is just a disturbance of particles

How do waves move?

Waves, such as sound and light, carry energy. When

light strikes matter, it may be absorbed, transmitted, or

reflected. Light may change direction when it moves from

one material to another

Types of Waves

Types of Waves

Have you ever dropped a rock into a pool of water?Waves spread out in all directions from the pointwhere the rock enters the water.

The rock causes molecules in the water to move backand forth as a vibration. A wave carries energy awayfrom a vibration

Do the “wave”!

Look at the movement below.

What do you see?When waves move through matter,the matter doesnotmove along with thewave, justlike the people move up and down but stay in the sameplace.

Transverse Waves

When transverse waves move through matter, they causethe matter to move in a direction different than thewave moves. If the wave is moving to the right,molecules in the matter move up and down. Focus onone particle and watch it move:

Compressional

Wave

If acompressional

wave is moving through matter, the matter moves backand forth in the same direction as the wave. The particles in the mattermove forward and then backward, over and over again.

An important type ofcompressional

waves is sound. As with all

waves, sounds are caused by vibrations. Think about what happens if

you strike your pencil against a desk. The force of your pencil causes

molecules in the desk and air next to it to vibrate. These vibrations

cause nearby air particles to vibrate, and they cause other molecules to

vibrate. The vibrations move outward through the air in all directions.

You hear sound when the vibrations reach your ear. You can also

hear the pencil striking the desk if you place your ear against the

desk. Sound waves can travel through matter, but they cannot travel

through empty space.

Compressional

Wave

Watch one particle and watch its direction of motion

Water Waves

Let’s see what Tim and Moby haveto say!

Electromagnetic Spectrum

Electromagnetic energy is created by vibration. This vibrationproduces waves that carry energy. Each electromagnetic waveemits (or gives off) a different level of energy. These energiestravel silently at the speed of light and produce a “signature”wave-with a unique range of length, energy, and frequency thatscientists can identify and measure. Electromagnetic waves areorganized in the ES by wavelength from the shortest (gamma) tothe longest (radio)

Frequencies

One way to measure the energy of an EM wave is bymeasuring the frequency. Frequency refers to thenumber of waves a vibration creates during a period oftime-like counting how frequently cars pass throughan intersection. In general, the higher the frequency,or number of waves, the greater the energy of theradiation.